John,

I am sorry you are going through this with your friend. ALS is a monster of a disease.

If your BIL is already on a ventilator, he is in a very fragile state. Being on the vent makes him more vulnerable to respiratory infections, so even a cold could be serious. Since he is on hospice, they may or may not choose to treat big infections, and a case of pneumonia could very well cause his death.

On the other hand, if he is stable and avoids infection, he could live much longer. It depends on so many factors.

I am glad hospice is involved. They will be a huge help to you all.

Good luck.